"The topic of employees' salaries is well guarded by most companies, so it's not always easy to figure out how your pay compares to your colleagues'," says Taylor. "If you're willing to invest the time and research or look for the signs, however, you'll be better informed as to whether you should ask for a raise or walk."

Here are 15 signs you're paid less than you should be:

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15 signs you're underpaid

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15 signs you're underpaid

1. A similar job listing on your company website offers higher pay

"If there are multiple positions like yours at the company, the job description closely resembles yours, and the salary is higher, that's one of the most obvious signs," says Taylor.

Stay on top of this by searching your own company's job postings every now and then to monitor what new employees are being paid, "and to see if that feels reasonable given your current level of experience and role in the company," adds Michael Kerr, an international business speaker and author of "The Humor Advantage."

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2. Your firm's revenue has taken off, but your salary has barely budged

If your company is private, it's harder to measure revenue growth vs. a public company.

"But you're likely having discussions about corporate growth with managers in your normal course of business," Taylor says. "This is an opportunity to dig deeper. If you're armed with the fact that the firm has seen 20% growth in one year, but your salary is under par, you'll strengthen your argument for a raise."

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3. Research tells you you're underpaid

This is a pretty solid sign.

"You must stay on top of the current salaries for your type of position," Taylor says. "There are many online sources for this, including PayScale.com, Glassdoor.com, Indeed.com and Salary.com."

Kerr says using an online salary calculator to see where average wages are or should be, for someone in your role and with your level of education and years of experience, can be a good starting point and may indicate if there's a discrepancy between your wage and the going rate.

(Kohei Hara via Getty Images)

4. The salary for your first job was below market, and it hasn't changed much since

Think back to the salary you accepted for your first job — maybe you accepted a salary you knew was low because you were desperate.

Now think about your progression from there. If your income hasn't changed much, you're probably underpaid.

"It can be difficult to play catch-up if you started low," Taylor says.

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5. You make less than your colleagues with similar levels of experience and education

Although people rarely talk openly about money — and in many companies are prohibited from doing so — there may be association or industry networking events where people who work in similar fields with similar levels of experience share anecdotes about their workplace and the topic of salary comes up, says Kerr.

"If the discussion makes your jaw drop, then there's a good chance you are being underpaid," he says.

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6. Your level of responsibility has increased, but your salary hasn't

"If your boss keeps piling on added duties, extra work, and especially more responsibilities without any increase in compensation or even a discussion about it, this may be a sign that you are underpaid," says Kerr.

Another sign: Your title has been upgraded, but it's not reflected in your paycheck, says Taylor.

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7. You're in a specialty area that's not in high demand

Some jobs are in higher demand than others.

"Cyber security and SEO/SEM marketing are hot job specialties, for example, whereas certain other positions are becoming more automated, or there may be great supply, but reduced demand," Taylor says. "Factor in where your field of expertise stands in the general job marketplace."

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8. Everyone around you seems to be getting bonuses — but you're not

Is there talk of annual bonuses, or performance bonuses, among your colleagues — but you've never received one yourself? You may want to look into this.

It may simply have been an oversight, but if was intentional, you should find out why you're not getting that extra money ... especially if you're confident that you deserve it.

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9. Your mindset is 'I'm just happy to be employed'

Have you fallen into a complacent mindset of being happy just to have a job? Most managers can sense this and will not go out of their way to make you an "absurdly happy" employee, if you're already a happy employee, Taylor says.

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10. You haven't had a performance review or raise in over a year

If it seems that the time for your performance review has come and gone — or it came without a raise — you might have reason to believe you're underpaid, says Taylor.

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11. You have a gut feeling

"If you feel inclined to take extra long lunch breaks, steal the occasional office supply, or in some other small way take advantage of something in your workplace because you feel you are 'owed' it, even at a subconscious level, this could be an obvious sign because at some level you feel underpaid," says Kerr.

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12. Your company has a high turnover rate

If there's high employee turnover despite there being a positive workplace culture, this can be a sign that wages in your organization in general are below what they could or should be, Kerr says.

13. You never negotiate your pay

14. Your boss is evasive when you want to discuss your career path

Do you find that it's impossible to discuss your long-term career growth with your boss? He or she may be reluctant because that may lead to a salary discussion or something complex that they're unprepared to discuss.

"That's not something you should be willing to sweep under the rug for very long, even if your boss is," Taylor says.

(Klaus Vedfelt via Getty Images)

15. Your salary increases are negligible

Perhaps you did get a raise last year or for the last two years, but they're in the 1% to 3% range consistently. Depending on your department, company, and industry, particularly if you're on the lower end of the scale, you may be underpaid, says Taylor: "A lot depends on the other feedback and information you're getting along the way."